The invention relates to a modular set of an outer shell for an artificial hip joint pan in accordance with the preamble of claim 1.
An outer shell for an artificial hip joint pan which consists of a hemispherical shell and lug parts which are projectingly arranged at its equatorial edge is known from the document EP-A-0 563 503. An outer shell of this kind is for example used when the acetabulum is damaged or strongly degenerate at the location to be carried, which is often the case in particular in revisions of implanted artificial joints. The lug parts are matched to the shape of the xe2x80x9cos iliumxe2x80x9d bone or the xe2x80x9cos ischiixe2x80x9d bone respectively during the implanting through plastic deformation and are afterwards anchored in a region capable of carrying by means of bone screws, so that the outer shell is firmly secured at the pelvic bone.
Disadvantageous is the fact that a large number of outer shells of different sizes is required. Disadvantageous in the known outer shell is in addition the fact that a relatively large opening at the operation field is required for the implanting. In addition the matching of the shape of the lug parts to the shape of the pelvic bone is difficult and complicated.
The object of the present invention is to propose an outer shell which is more economical and simpler to implant.
This object is satisfied with a modular set of an outer shell having the features of claim 1.
Subordinate claims 2 to 9 relate to further advantageous embodiments of the outer shell.
The object is satisfied in particular with a modular set for an outer shell comprising a shell-shaped outer part and an anchoring aid which is designed as a lug, a spike or a hook, with the shell-shaped outer part having at its equator an end surface with bores, and with each anchoring aid having a securing part which is designed to be matched with respect to the end surface in such a manner that the securing part can be secured at the shell-shaped outer part by means of screws which engage in the bore.
The modular construction of the outer shell in accordance with the invention has the advantage that the modular set comprises a plurality of differently shaped, shell-shaped outer parts and/or anchoring aids so that it is left up to the surgeon to decide during the operation which shell-shaped outer part and/or which anchoring aids are best suited for the anchoring in accordance with the state and the anatomy of the pelvic bone. Since the outer shell can be assembled on site in the operation field, the opening of the operation field can be kept small, which for example has a protective effect on the soft parts. After the introduction of the shell-shaped outer part a suitable lug can be selected and applied to the pelvic bone in the operation field. The lug advantageously has a shape which is pre-formed to the anatomical shape of the pelvic bone. Should it turn out in the matching of the lug to the pelvic bone that their mutual shapes do not agree ideally, then the lug can be removed again from the operation field and be reshaped outside the operation field with suitable tools. As far as required the process of the laying on of the lug at the pelvic bone and the reshaping can be repeated a plurality of times. As soon as the lug has the desired anatomical shape the lug can be firmly connected to the shell-shaped outer part with the help of a screw. The ideal choice of the lug shape, the lug size and their kind of anchoring in the pelvic bone is of importance for the reliable, long term anchoring of the outer shell, in particular when the pelvic bone has larger defects such as holes. In addition the shell-shaped outer part can also be chosen in accordance with the defect of the pelvic bone. For example round or ovally designed outer parts are available to be chosen from. It proves for example to be particularly advantageous in the event of a large hole in the pelvic bone to choose a correspondingly large outer part in order to fill the hole with the implant, which stabilises the bone.
Should it turn out during the implanting that the lug is not suitable or additional anchoring aids are required for the fixing of the outer part, then for example a spike or a hook can be used as a further anchoring aid.